This invention relates to a queue device for use in carrying out advanced control in a digital computer, a microprocessor, or the like.
A conventional queue device of the type described serves to preliminarily fetch and buffer successive digital signal units, such as instruction code units or data units, prior to execution of each digital signal unit to successively produce output digital signal units one by one. For this purpose, the conventional queue device is intermediate between a control unit and an execution unit and comprises a first-in-first-out memory device having first through last memory stages. In the first-in-first-out memory device, the digital signal units are successively memorized in the first memory stage of the first-in-first-out memory device one at a time as a memorized signal unit. Each memorized unit is successively shifted to the last memory stage to be supplied to the execution unit as each of output digital signal units which may often be called readout digital signals. In this event, each output digital signal unit has the same length as each of the first through last digital signal units. This means that each output digital signal unit fixedly has a single word length when each of the digital signal units is composed of a single word length.
It should be noted in this connection that each of the instruction code units or the data units does not always have a single word length but often has a variable word length, such as a double word length, a triple word length, or the like. Inasmuch as each instruction unit or data unit should be supplied to the execution unit at every word, the queue device must supply the execution unit with each instruction unit or data unit at every word two times or three times when each digital signal unit has a double word length or a triple word length. Therefore, it takes a long time to send each instruction or data unit from the queue device to the execution unit. This results in a reduction of performance in an information processing system comprising such a queue device.